This invention relates to a sharpening system for saw chains and, in particular, to such a sharpening system for sharpening the cutters on saw chain as that chain is being driven by the chain saw motor means.
There have been numerous proposals for saw chain sharpening devices mounted directly upon a chain saw to eliminate hand-filing of the chain cutters. Examples of such proposals can be found in the following patents: Muir U.S. Pat. No. 3,138,973; Tupper U.S. Pat. No. 3,465,795; Oehrli U.S. Pat. No. 3,260,287; and Oehrli U.S. Pat. No. 3,301,098.
Of the numerous prior suggestions, many have involved a provision of a grinding stone that is manually movable from a retracted position to a position for engagement with the cutters on a moving saw chain. Commercial acceptability of such systems has been quite limited for a number of reasons. Principal among such reasons has been the difficulty of achieving an inexpensive sharpener assembly that is capable of very precise positioning of the grinding stone relative to the chain cutters. Other difficulties have included the fouling of elements of the sharpener assembly by saw dust or other debris, thereby interfering with its proper operation at the time that sharpening of the cutters is required.